The subject matter of this invention relates to metal-containing organosiloxane amine copolycondensates which exhibit a random, block-shaped or mixed distribution of the components in a polymer matrix. The shaped or formed polysiloxanes containing Pd, Pt, Ru and/or Rh exhibit an advantage in the areas of methodology and application technology, in that these shaped, polysiloxanes have a macroscopic spherical form and constitute valuable catalysts, especially for hydrogenation and oxidation reactions. Especially preferred properties of the heterogenous catalysts in accordance with the invention are the very good physical properties, as well as the high reproducibility of the organopolysiloxane carrier. Furthermore, methods are described according to which these products may be produced and used.
Heterogeneously used noble-metal carrier catalysts for use in hydrogenation and oxidation reactions are prepared according to the state of the art by applying a noble metal partially in elemental form, but primarily in the form of a compound, onto a suitable catalyst carrier. If the metal is deposited in the form of a compound, the metal-charged carrier must be subsequently subjected to a reductive treatment.
The reduction may occur in conjunction with the application of the metal in the liquid phase by means of a treatment with a reducing agent, such as a hydrazine. Alternatively, the reduction may take place after drying by means of a treatment with hydrogen at a rather high temperature in the gas phase. As another alternative, the reduction may take place immediately before or during the catalytic use in the reaction medium. Commonly used carriers for this purpose are activated carbon and inorganic materials, such as aluminum oxide, silica gel or zeolites (see K. H. Schmidt, Chemische Industrie (1984), pp. 380-388, 572-576, and 716-718).
Some of the disadvantages of these carrier materials are the deficient reproducibility of the physical and chemical properties (for example, in the case of activated carbon); the partially unsatisfactory physical and mechanical properties; the fact that they are unformed as a rule and must be formed subsequently; and very importantly, their deficient functionality, via which no control of the metal dispersity and the catalytic properties are possible. The last disadvantage named above is often present in such a manner that a chemical posttreatment (e.g. poisoning with sulfur) is necessary to adjust certain catalytic properties.